A typical air heater for a fluid catalytic cracking unit comprises a gas burner for heating a large mass of high velocity turbulent air under several psig (pounds per square inch gauge) pressure from a powerful air blower and for supplying the heated air to a regenerator of a fluid catalytic cracking unit during startup of the unit. The main burner is lighted for a gas fired pilot which has previously been lighted from an electrical spark igniter. The usual and average time of 10 hours, with a maximum of 24 hours has been required by operators in the past to successfully light the pilot and have it stay lighted until the main burner can be lighted. This is due to the trial and error method of adjusting the fuel to arrive at a combustible mixture with the air available at the burner in the heater and the ease in which the flame can be blown out due to the tremendous turbulence of the air in the heater.
The disclosed turbulent air heater provides a precise pre-mix of compressed air and fuel gas in the combustible range for the pilot, with the correct combination of restrictive orifices and upstream pressure settings and particularly for air heater pressures not exceeding 15 psig, for example.